Increasing the acceptance and use of electric vehicles provides an environmentally responsible solution for reducing air pollution and addressing the transportation needs of society while not adversely impacting the existing transportation infrastructure. One of the greatest hurdles to increasing the acceptance of battery powered vehicles is the inherent limitations in energy storage density possible using currently available battery technologies. The relatively limited energy storage density of a battery limits the practical range of battery powered vehicles to several hundred miles. The relatively slow recharge rate for batteries requires a battery powered vehicle stop for an hour of recharging for every two to three hours of travel time.
Wireless (or inductive) charging of vehicular secondary cells (e.g., rechargeable batteries) may permit reducing the rate of depletion of a vehicular battery while the vehicle remains in motion. With sufficient available power, an inductive charging system may even recharge a vehicular battery while the vehicle is motion. Thus, a more widespread adoption of wireless charging technologies is limited due technology concerns such as: the relatively poor efficiency of wireless power transfer; and, the high leakage radio frequency (RF) electromagnetic field exposure to users, particularly occupants of a vehicle.
Previous solutions have targeted increasing the power supplied to the power receiving unit in the vehicle by boosting the current supplied to the power transfer unit external to the vehicle. While such solutions may increase the power received by the power receiving unit in the vehicle, such a solution does nothing to improve the power transfer efficiency between the power transmission unit and the power receiving unit and thus does so at the expense of additional wasted power. Another solution is to increase the coupling between the power receiving unit and the power transmission unit by adding turns to the coil in the power transmission unit using a high quality-factor (i.e., a “high Q”) material. High-Q materials are usually costly and thus, generally not economically feasible for widespread implementation. Additional options may include plating standard coils with high-Q materials such as silver and fabricating coils in elaborate geometries.
Although the following Detailed Description will proceed with reference being made to illustrative embodiments, many alternatives, modifications and variations thereof will be apparent to those skilled in the art.